Chromium-nickel steel.



Patented August 4, 1903.

PATENT OFFICE.

ROBERT A. HADFIELD, OF SHEFFIELD, ENGLAND.

CHROMIUM-NICKEL STE EL.

SPECIFICATION forming part of Letters Patent N 0. 735,666, dated August 4, 1903.

Original application filed March 19, 1898, Serial No- 674,497. Divided and this application filed June 5,1903. Serial No. 160,177. (No specimens.)

To all whom it may concern.-

.Be it known that 1, ROBERT A. HADFIELD, a subject of the King of Great Britain, and a resident of Sheffielthcounty of York,England, have invented an Improvement in Chromium- Nickel Steel, of which the-following is a specification.

This invention relates to a hard steel which can be produced at a comparatively low cost and which possesses superior qualities and which can be cast, rolled, and forged like other hard steel, having special susceptibility to hardening, with less liability to watercracking than usual, as for instance frequently occurs with ordinary steel, the steel to be hereinafter described being particularly suitable for use in the production of articles of comparatively large sectional area that are required to be hardened in the mass-thatis to say, practically throughout their section.

One exceedingly useful employment of my novel steel is in the production of projectiles possessing great strength and penetrative powers and specially suitable for armor-piercing and like purposes.

The steel forming the subject-matter of this application is described in my application Serial No. 67 4,497, for process of making chromium-nickel steel, filed March 19, 1898, from which application this present application is a division.

In carrying out my invention I add to a suitable basis of iron, say, about 0.75 per cent. to one per cent. of carbon, two per cent. of chromium, and two per cent. of nickel, care being taken to keep the amount of manganese that may be present at least under 0.3 per cent. and preferably as much lower as possible, as I have found in my experiments that the presence of manganese much in excess of the quantity mentioned causes watercracking when the steel is hardened. For this reason I regard manganese as a deleterious substance in hard steel and one the presence of which should therefore be avoided as far as possible.

The percentage of carbon, chromium, and nickel may be varied to some extent from those hereinbefore mentioned provided the resulting product is nearly free from or low in manganese and capable of being readily hardened. Thus the carbon might vary from 0.60 per cent. up to 1.75 per cent, the chromium from about 0.25 per centiup to five per cent. and the nickel from about 0.25 per cent. upto seven per cent. I have, however, obtained the best results for articles of comparatively large mass with the proportions first-mentioned, manganese being practically absent in the resultant product.

A solidifying agent may be added to the steel, preferably in a molten condition, for the purpose of obtaining soundness and freedom from blow-holes. Silicon or aluminium, either or both, may be used as the solidifying agent, and when used the silicon may vary in quantity up to about 2.50 per cent, though preferably for most purposes smaller quantities-say of about 0.30 per cent.are sufficient, while the aluminium may vary up to about 0.20 per cent, but preferably for most purposes not more than 0.10 per cent. will be necessary.

A suitable basis of iron for making my improved steel is decarbonized iron produced by any suitable steel-making process and as free as possible from manganese. J

The carbon,chromium,nickel, and the solidifying agent may be added in various forms. For example, the carbonizing physio may be in the form of a suitable carbonaceous material-as, for instance, white iron of good pure quality, low in sulfur and phosphorus, and practically free from manganese. The chromium and nickel may be added in the metallic form or in the form of ferrochromium and ferronickel, respectively. Aluminium may be added in the metallic state or in the form of ferroaluminium and the silicon in the form of ferrosilicon. I prefer to add the carbonaceous material and chromium and nickel either as metals or alloys in a melted state to the molten iron in order to facilitate thorough admixture therewith, and so,too,the solidifying agent should be added in a melted state.

In carrying out my invention I take iron such, for instance, as is now used in the production of acid-steel and decarbonize it, pref-- erably by the pneumatic method,in a suitable Vessel or converter, though it may be by treatment in the ordinary way in an open-hearth IOU furnace, care being taken in either case to eliminate practically the whole of the carbon, manganese, and silicon it may contain. To the molten iron thus obtained I add the decarbonizing physic, chromium, and nickel, as hereinb'efore described, and preferably also the solidifying agents-what is, aluminium and silicon, either or both. The manner of making these additions is of the greatest importance in producing steel of special high quality, and I proceed as follows, viz: The carbonizin g physic is melted in crucibles or in a furnace which is not subject to oxidizing influence, and the molten physic is run into a ladle. Upon the physic the decarbonized iron, as described, is then poured. The addition of the physic in the furnace itself is objectionable because oxidizing infl uences are at once at work, and consequently steel of such uniformity as I produce cannot be obtained.

It is extremely important in order to obtain a satisfactory result that the various additions be made with accuracy, and for this reason they (the additions) should not be made to the molten iron while the latter is in the converting vessel or furnace, as by such procedure it is difficult toinsure that the resulting steel shall contain the desired exact proportions of the added substances and shall be of uniform quality. To obviate this difficulty, I prefer to run successively into a ladle or vessel carried by a suitable weighing-machine, such as a Denison weighing-machine or a platform weighing-machine, the desired amounts of carbonizing physic, chromium, nickel, and the solidifying agent, each in a suitable form or condition, such as hereinbefore described, and in a molten state. The desired weights of the several substances, preferably previously melted in crucibles, are thus ascertained in a ready and very exact manner. Into the weighed molten contents of the ladle while the latter is carried by the weighing-machine is then run, preferably direct from the furnace, so much of the molten iron as will increase the weight of the contents of the ladle to that of the required quantity of my special steel, which is then either run off into ingots, which can be afterward forged into articles of desired shape, or it is poured into suitable molds to produce castings.

I have found the commonly-accepted idea that manganese is necessary in steel is to a large extent erroneous, and, in fact, its presence is in many ways very deleterious.

In making special high-quality steel that is, hard steels containing, say, 0. per cent. to one per cent. of carbon-I find that the lower the manganese is kept the better the product; but when the material is not required to possess hardness primarily-27. c., natural hardness or capacity for subsequent hardening the advantage to be gained is not so great,

words, manganese may not be objectionable in mild steels-say under about 0. 35 per cent. carbonbecause in such cases(and they probably represent the majority of uses for which steel is required) the action of the carbon is so much weakened that more or less manganese is immaterial.

Manganese is in itself a very hard and brittle metal, and while this in itself may not be an objection, yet I consider that in its action as a carbid of manganese when carbon is pre. ent it is most harmful when the special qualities of hardness and toughness are requisite, believing that these qualities cannot be developed if manganese is present in quantity say over 0.25 per cent. It is to be borne in mind, however, that I am not referring to large percentagessuch as in Hadfield manganesesteel alloys containing over two per cent. up to twenty per cent. manganese, of which I am the inventor and which come under an entirely different category.

Heretofore, so far as I am aware, it has not been known that sound ingots, sound both as regards freedom from unsoundness-that is, honeycombed-and sound as regards forging-that is, free from cracks or other forging defectscould be obtained without the presence of manganese, particularly if silicon or aluminium, or both, be used; but, as herein before set forth, I have discovered this fact and that with suflicient silicon or aluminium, or both, no manganese is required, while the resultant product can be rolled and forged like other hard steels and hardened and tempered readily, with the cracking not only no more, but actually less than with the most expensive crucible-steels.

I find that with practically no manganese the steel while hardening equally as well as heretofore is much tougher and shows a better-looking fracture, all of which goes to show that the absence of manganese has prevented the formation of the very objectionable brittle carbid of manganese. Furthermore, I have found that by eliminating the manganese in my improved steel or keeping it low in quantity, as set forth, it is not necessary to employ high-quality stock or raw material for the production of my special alloy or improved steel. Thus while it has heretofore been necessary in the production of hard steel of good quality to employ the very highest quality of raw material, such as Swedish pig or melting iron, I find that in producing steel according to this invention, in which the manganese is kept low, hard steel of superior quality can be produced containing a larger proportion of sulfur and phosphorus than would be admissible if manganese were present in much larger quantity. Consequently I am able to use cheap raw stock, such as ordinary hematite pig-iron or even mixtures of ordinary pig-iron and steel scrap, to form a suitable basis of iron for forming my improved steel. Thus whereas high-quality raw material containing sulfur and phosphorus only-say up Such a basis of iron must of course be decarbonized, demanganized, and desiliconized, as hereinbefore described, before mixing the carbon, chromium, and nickel therewith, suf: ficient silicon or aluminium, or both, being also added to decompose any oXid there may be present. This latter addition is important, because there will be little or no manganese present for effecting such decomposition.

Having fully described my invention, what I claim as new, and desire to secure by Letters Patent, is

' 1. The herein-described steel low in manganese, containing not more than 0.2 per cent. thereof, and capable of being hardened in the mass, and containing not more than 1.75 per cent. carbon, chromium up to five per cent, and nickel up to seven per cent.

2. The herein-described steel, having a high percentage of carbon and low in manganese, capable of being hardened in the mass and suitable for direct casting of hollow projectiles and the like, containing not less than 0.6 per cent, nor more than 1.75 per cent. of carbon; not less than 0.25 per cent., nor more than five per cent. of chromium, and not less than 0.25 per cent. nor more than seven per cent. of nickel.

3. The herein-described hard steel, containing from 0.7 to 1.1 per cent. of carbon, 1.7 to 2.2 per cent. of chromium; 1.8 to 2. 5 percent. of nickel, not -more than 0.2 per cent. of manganese, and a solidifying agent.

4. The herein-described hard steel, contain ing from 0.7 to 1.1 per cent. of carbon; 1.7to 2.2 per cent. of chromium; 1.8 to 2.5 per cent. of nickel, not more than 0.2 per cent. of manganese, and a solidifying agent, the latter containing about 0.2 per cent. of aluminium and about 2.5 per cent. of silicon.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

' ROBERT A. HADFIELD.

\V-itnesse's NATHAN HEARD, H. O. LUXBURY. 

